EP0748116B1

EP0748116B1 - television receiver

Info

Publication number: EP0748116B1
Application number: EP96113700A
Authority: EP
Inventors: Hideaki Inoue; Kiyoshi Ohhashi; Asahiko Okada; Takashi Sabato; Tomio Shiota
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 1992-11-18
Filing date: 1993-11-16
Publication date: 2001-02-07
Anticipated expiration: 2013-11-16
Also published as: EP0748116A1; KR940013187A; EP0598391A3; US5455867A; DE69329925T2; DE69329918T2; DE69329925D1; DE69329918D1; CN1050491C; CN1089772A; KR0126896B1; EP0598391B1; EP0598391A2

Description

Field of the invention

The present invention relates to a television receiver including a cathode ray tube and a speaker apparatus, as set forth in the preamble of claim 1. A television receiver of this kind is known from EP- A -0 451 991.

Background of the Invention

An acoustic apparatus disposing a horn or an accoustic pipe before a speaker leading the sound waves emitted by the speaker to an opening has been widely used hitherto because of the advantages as compared with the constitution without using a horn or an acoustic pipe, such as acquisition of high sound pressure output and radiation of sound waves in a specific direction.
In the known television receiver incorporating such speakers, an acoustic pipe mounting a speaker is disposed along the left and right sides of the cathode-ray tube for image display, and the television cabinet is located along the acoustic pipe, so that the television receiver is small and slim.
Inside each acoustic pipe, absorption members and reflection plates are disposed depending on the length and shape of the acoustic pipe, and the acoustic characteristic is improved.
In such apparatus, as a result of too much attention paid to the small and slim structure of the receiver, the area of the section and opening of the leading part for guiding the sound waves from the acoustic pipe is too narrow, which has influenced the acoustic quality and lowered the output sound pressure.
In an apparatus having a bass-reflex port for bass register for enhancing the bass register disposed closely to the acoustic pipe, interference of radiation sound wave from the acoustic pipe occurs, which has caused sound pressure frequency characteristics of extreme peak dip.
Besides, for the purpose of downsizing, the magnetic circuit of the speaker is too close to the cathode-ray tube, and the image is disturbed by the leakage magnetic flux from the magnetic circuit.

SUMMARY OF THE INVENTION

It is hence a primary object of the invention to present a speaker apparatus useful for making small and slim a television receiver, and a television receiver using the same.
It is other object of the invention to present a television receiver having a speaker apparatus useful for output of high sound quality and high sound pressure.
This object is achieved by the features of claim 1. Preferred embodiments of the invention are subject matter of the dependent claims.
According to a preferred embodiment, the weight is reduced without giving adverse effects on the picture quality by approach of a speaker magnetic circuit to a cathode-ray tube in the trend of small size and slim body of the television receiver.

Fig. 1: is a perspective partial view of a television receiver incorporating an embodiment of a speaker apparatus according to the invention.
Fig. 2: is a magnified view around a bass-reflex port for enhancing the bass register in Fig. 1.
Fig. 3: is a comparative diagram of sound pressure and frequency characteristics of the invention and the prior art.
Fig. 4: is a plan sectional vie of a television receiver incorporating a preferred embodiment of a speaker apparatus according to the invention.
Fig. 5: is a sectional view showing the constitution of the speaker in Fig. 4.
Fig. 6: is a sectional view of a magnetic circuit of the speaker in Fig. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference is made next to Fig. 1. This is a perspective view of an embodiment of a television receiver and a speaker apparatus according to the invention.
In Fig. 1, at the front side of a speaker 31 for radiating sound waves, an acoustic pipe 33 for guiding sound waves and having a slender and nearly rectangular opening 32 is disposed. A bass-reflex port 35 for enhancing the bass register having an opening 34 is disposed closely to one side of a rectangular side wall 36 delimiting the acoustic pipe 33. The acoustic pipe 33 and the bass-reflex port 35 for enhancing the bass register are coupled together by means of said wall 36 shared by the both, and a sound absorption material 37 for forming the remaining portion of the wall of the bass-reflex port 35 for enhancing the bass register. That is, at least part of the wall for composing the bass-reflex port is made of sound absorption material. Inside the acoustic pipe 33, a sound absorption material 38 is disposed, and a reflection plate 39 is also provided. A tweeter 40 for reproducing the treble register is provided in the sound wave passing route of the speaker 31.
Refer to Fig. 2. This is a magnified view near the bass-reflex port 35 for enhancing the bass register shown in Fig. 1.
Refer then to Fig. 3. This is a comparative diagram of the sound pressure and frequency characteristics of the speaker apparatus of the invention and the speaker apparatus employing the conventional acoustic pipe, in which the characteristic curve a denotes the conventional speaker apparatus, and the characteristic curve b represents the invention. In both speaker apparatuses, the opening of the acoustic pipe is a slender rectangular form, and the opening of the bass-reflex port for enhancing the bass register is disposed closely to the opening of the acoustic pipe.
The sound waves radiated from the bass-reflex port for enhancing the bass register contain not only low frequency components but also medium and high frequency components. Since the phase relation with the medium and high frequency components radiated from the opening of the acoustic pipe is not constant, enhancing and canceling of the synthesized sound pressure of the both occur, and a sound pressure and frequency characteristic extreme in the difference between the peak and dip as indicated by characteristic curve a in Fig. 3 occurs.
In the television receiver and speaker apparatus of the invention, the sound absorption material 37 disposed near the front opening of the bass-reflex port 35 for enhancing the bass register acts to eliminate the stationary waves occurring inside the acoustic pipe 33, and absorb the medium and high frequency components radiated from the bass-reflex report for enhancing the bass register, and hence there is no interference to the medium and high frequency components radiated from the opening 32 of the acoustic pipe 33, so that a flat sound pressure-frequency characteristic as in characteristic curve b in Fig. 3 is obtained.
Besides, the sound absorption material 37 also acts to remove stationary waves inside the acoustic pipe 33, and therefore the more natural acoustic reproduction which was extremely difficult in the conventional apparatus is realized without attenuating the low frequency components radiated from the bass-reflex port 35 for enhancing the bass register.
In the shown embodiment, incidentally, the bass-reflex port 35 for enhancing the bass register is composed of the same wall surface as the wall surface of the acoustic pipe 33, but same effects are obtained by composing to dispose the bass-reflex port 35 for enhancing the bass register closely to the acoustic pipe 33.
Also in the shown embodiment, the bass-reflex port 35 for enhancing the bass register is disposed at one side of the acoustic pipe 33, but similar effects can be achieved when disposing the bass-reflex port 35 for enhancing the bass register at both sides of the acoustic pipe 33.
As described herein, in the television receiver, as is clear from the drawings, the acoustic pipe having a nearly rectangular section for guiding the sound waves is disposed, and part of the wall of the bass-reflex port for enhancing the bass register is disposed closely to one side or both sides of the wall of the acoustic pipe by using a sound absorption material, so that the television receiver may be further reduced in size and thickness, while acoustic reproduction of high sound quality and high sound pressure is realized.
Reference is made next to Fig. 4. This is a plan sectional view showing the outline of a television receiver incorporating a preferred embodiment of a speaker apparatus according to the invention.
In Fig. 4, at the front side of a speaker 61 for radiating sound waves, an acoustic pipe 62 having a slender and nearly rectangular opening for guiding sound waves is disposed. The speaker 61 has a magnetic circuit 63 which is an important element. The television receiver is represented by a cabinet 64 and a cathode-ray tube 65 for the sake of simplicity.
Fig. 5 is a sectional view showing the construction of the speaker 61. In the diagram, the magnetic circuit 63 is composed of a columnar center pole 71, a plate 72 mounting the center pole 71 in the middle of the yoke of the bottom, a ring-shaped magnet 73 mounted at the inner side of the upper part of the plate 72, and a magnetic gap 74.
A frame 75 is fixed on the magnetic circuit 63, and in the open peripheral part of the frame 75 there is affixed the outer circumference of a diaphragm 77 having a voice coil 76 moving up and down without contact in the magnetic tape 74 coupled in the central part. The voice coil 76 is supported by a damper 78, and a dust cap 79 is adhered to the diaphragm 77 above the voice coil 76.
Fig. 6 is a sectional view of the magnetic circuit 63, showing the line of magnetic force of the magnet 73 magnetized in the radial direction, and a leakage magnetic flux 82. As is clear from Fig. 6, in thus composed magnetic circuit 63, the line of magnetic force of the magnet 73 passes through the magnetic gap 74 while hardly escaping outside.
In this preferred embodiment, as shown in Figs. 4 to 6, the speaker 61 is composed by forming the magnetic circuit 63 greatly reducing the leakage magnetic flux 82 by using the ring-shaped magnet 73, magnetized in the radial direction, and the acoustic pipe 62 having a slender opening and rectangular form for guiding the sound waves is coupled to the speaker 61, and is disposed closer to the cathode-ray tube 65 of the television receiver, and this is made possible by the fact that the effect of the leakage magnetic flux 82 from the magnetic circuit 63 on the cathode-ray tube 65 can be practically ignored. Therefore, by using the speaker apparatus according to the invention, the receiver is slimmer, and it is also possible to mount on a Hi-Vision receiver of an extended screen with a large aspect ratio, and Hi-Vision receiver of high sound quality and high grade can be presented.
Moreover, the constitution of the magnetic circuit 63 is simple, and the shield cover for prevention of leakage magnetic flux is not needed, thereby contributing to reduction of weight.

Claims

A television receiver including a cathode-ray tube, a cabinet and a speaker apparatus, said speaker apparatus comprising:
a speaker (31), an acoustic pipe (33) disposed at the front side of the speaker (31) and extending to the front side of the cabinet, at least one bass-reflex port (35) for enhancing the bass register and disposed closely to the acoustic pipe (33), wherein the constitution composed of the acoustic pipe (33) and the bass-reflex port (35) possesses a slender rectangular front opening (32), and the front opening (34) of the bass-reflex port (35) is disposed closely to the front opening (32) of the acoustic pipe (33), and the portion of the acoustic pipe (33) and the bass-reflex port (35) joining to their respective front openings (32,34) are adapted to the shape of the space between the outer wall of the cathode-ray tube and the inner wall of the cabinet,
characterised in that
said constitution comprises a common wall (36), common to said bass-reflex port (35) and said acoustic pipe (33) and coupling together said bass-reflex port (35) and said acoustic pipe (33), wherein
at least a part of said common wall (36), which part is disposed near said front openings (34,32), is made of a sound absorption material (37) to eliminate the stationary waves occurring inside the acoustic pipe (33) and to absorb the medium and high frequency components radiated from the bass-reflex port (35) for enhancing the bass register.
The television receiver as set forth in claim 1, wherein the space for composing the acoustic pipe (33) and the space for composing the bass-reflex port (35) are partitioned by a partition board, of which at least a part is made of said sound absorption material (37).
The television receiver as set forth in claim 1 or 2, wherein the magnetic flux of the magnetic gap (74) where the voice coil (76) of the speaker (61) is accommodated is supplied by a ring-shaped permanent magnet (73) magnetised in the radial direction.